Floatable safety cover for swimming pools

ABSTRACT

A platform of perforated, semi-rigid sheet material is supported on a frame of rigid, pressure-tight tubing. The shape of the platform corresponds to the perimeter of the water surface in the protected pool. The platform, in its operating position, is supported by a number of inflatable floatation pillows whose displacement is varied by the control of the pressure level of compressed air entrapped therein. The tubular frame serves as distribution manifold for the compressed air and is connected to a pressure-sensitive alarm device. The alarm device provides an audible warning signal whenever the excess buoyancy of the platform drops below the weight of a person accidentally stepping thereon.

Elite States 'lroiano atet H 1 FLOATABLE SAFETY COVER FOR SWIMMING POOLS [76] Inventor: Daniel A. Troiano, 9- Pam Dr..

Commack, NY. 11725 [22] Filed: June 19, 1972 [21] Appl. No.: 264,386

[451 June 4, 1974 Glenn 4/l72.l3 Madden 4/l72.l3

[5 7 ABSTRACT A platform of perforated, semi-rigid sheet material is supported on a frame of rigid, pressure-tight tubing. The shape of the platform corresponds to the perimeter of the water surface in the protected pool. The platform. in its operating position, is supported by a number of inflatable floatation pillows whose displacement is varied by the control of the pressure level of compressed air entrapped therein. The tubular frame serves as distribution manifold for the compressed air and is connected to a pressure-sensitive alarm device. The alarm device provides an audible warning signal whenever the excess buoyancy of the platform drops below the weight of a person accidentally stepping thereon.

15 Claims, 18 Drawing Figures PATENTEDJUN 41914 31313704 SHEET 5 UP 5 I F LOATABLE SAFETY COVER FOR SWIMMING POOLS BACKGROUND OF THE INVENTION The invention relates to pool covers whose primary function is the prevention of accidents connected with unattended swimming pools, particularly those located in unfenced yards of residential areas.

Such pools, whose number has been growing at a steadily increasing rate, present an unfortunate attraction to persons, particularly children, at times when competent supervision is not available. Experience has shown that neither fences nor the commonly employed fabric pool covers can prevent access to such pools, or offer protection to those who accidentally stray into them.

Many inventions in the prior art employ platforms which normally rest on the bottom of the pool and are raised to the surface. or suspended above the surface, when it is desired to render the pool inaccessible. These inventions ahve proved to be too complicated, cumbersome. expensive, or too restricted in applicability, to find commercial success.

It is. therefore, the primary purpose of the instant invention to teach the construction ofa safety pool cover for swimming pools simple in structure and adaptable to all manner of pools and all planform shapes and bottom configurations.

It is a further objective ofthe invention to teach operating and control means for a swimming pool safety cover whose working is readily undertaken by the average person and which provides warning of the approach of a potentially unsafe condition.

It is yet another objective of the invention to describe constructional details and materials which render the manufacture and installation of such safety pool covers economical.

SUMMARY The above objectives are attained by providing a safety cover for pools in which the upper surface, or platform, is manufactured from a water-permeable sheet of sufficient rigidity to support the weight of the average adult and of a material not subject to deterioration in contact with water; perforated hardboard and expanded metal screen being examples of suitable materials.

The platform formed by the aforementioned sheet is mechanically supported on a frame of rigid tubing, serving as a continuous manifold, throughwhich compressed air is distributed to the floatation members. These floatation members are constructed from vulcanized rubber sheet, or a similar impermeable and elastic membrane. made into pressure-retaining pillows by sealing the corresponding edges of two identical sections.

In plan view the platform is tailored to the shape of the particular pool to be protected with the support frame and the floatation bags underneath the platform. With the floatation members in the collapsed condition, the safety cover has a higher density than the water in the pool and will sink below the surface until it rests on the pool bottom. Should it be necessary, ballast will be provided to achieve negative buoyancy. The floatation members are so sized and distributed that upon inflation that platform acquires excess positive buoyancy and rises to the surface of the pool, and, in the latter position, is capable of supporting a predetermined weight without sinking.

The safety cover of the instant invention may be also modified to adapt to swimming pools having non-level bottoms, as will generally be the case in pools equipped with diving boards or with a wading section for children. In such cases, the platform is subdivided into the requisite number of sections, conforming to the substantially planar sections of the pool bottom, each of these sections being supported on its individual frame of tubular material. The several sections are jointed with flexible or rotatable elements to permit the safety cover to conform to the contours of the pool bottom in the submerged position and to assume a flat, continuous upper surface when floated.

Inflation of the floatation members is preferably by means of compressed atmospheric air provided by a compressor mounted near the pool and discharging, through a non-return valve, into a plenum chamber. The tubular framework of the safety cover, serving as the air distribution manifold, is connected to the plenum and to a relief valve, for releasing the air from the floatation pillows when the cover is to be submerged. A pressure-sensing alarm system may be provided at the plenum to give an audible or visible danger signal should the pressure level drop to a point at which the excess buoyancy of the safety cover becomes inadequate for its life-saving purpose. Control devices may also be provided to restart the compressor and reestablish the desired buoyancy automatically.

To prevent excessive list of the pool cover, as well as to reduce mechanical friction and to prevent damage to the pool walls, it is desirable that the safety cover be provided with guide rods on which bushings attached to the frame ride as the cover travels from the operative, or floating, to the inoperative, or submerged, position or vice versa. The guide rods also permit the provision of simple and sturdy means for anchoring the safety cover in the floating position; providing additional safety when the pool is to be left unattended or unused, in winter for example, for any length of time.

Other features and further advantages of the invention will become apparent with reference to the description of the preferred embodiment illustrated on the accompanying drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

In the accompanying drawings:

FIG. 1 is a perspective view of a rectangular swimming pool fitted with a safety pool cover of the instant invention;

FIG. 2 is a plan view of the inflation and control chassis of the embodiment of FIG. 1;

FIG. 3 is a sectioned view of the pool and cover of FIG. 1, taken along section line 3-3;

FIG. 4 is a sectional detail of the arrangement of guides and securing means of the safety cover, taken along section line 4-4 of FIG. 1;

FIG. 4 is a base view of a pool cover similar to that illustrated in FIG. 1;

FIGS. 6 and 7 are partially sectioned perspective and base views, respectively, of another embodiment of the safety pool cover, incorporating a pierced rigid platform;

FIG. 8 is a sectioned elevation of a swimming pool with a two-level bottom, showing an articulated safety pool cover of the instant invention in the fully submerged position;

FIG. 9 is a base view of the pool cover of FIG. 8, in the deployed position;

FIG. 10 is a partial section through the cover of FIG. 8, taken along section line 1010 of FIG. 9;

FIG. 11 is a detail showing the interconnection of the air distribution manifold and a floatation member;

FIGS. 12, 13 and 14 are views of an alternative articulated joint for use in sectioned safety pool covers;

FIGS. 15, 16 and 17 are details indicating alternative embodiments of anchor means for locking the pool cover to the guide rods; and

FIG. 18 is a section through a manual pressure release valve employed in the control system of the safety pool cover.

DESCRIPTION OF THE PREFERRED EMBODIMENT:

In the perspective view of FIG. 1 a safety cover 1 is shown covering the water surface in a rectangular swimming pool 10. The pool 10 is of poured concrete construction and is of the type normally installed with its perimeter 9 flush with the ground. The pool cover is operated by means of compressed air and control chassis 20 is provided, connected to the pool by means of conduit 26.

The control chassis 20 incorporates an air compressor 21, with its drive motor 22 and control switch 23, a plenum chamber 25, receiving air from the compressor 21 by means of hose 24, manual release valve 90, and a pressure sensitive alarm 28. For greater convenience and safety the chassis 20 may be located at some distance from the pool. The relative arrangement of its components is shown in the plan view of FIG. 2.

The alarm 28 is set by the advance ofa cam 72 bearing on push-button 74; the cam 72 being borne of the piston-rod ofa pneumatic cylinder 71 subjected to plenum pressure. Should a leak, or unauthorized actuation of the release valve 90, cause a reduction in air pressure in the plenum 25, the cam 72 retracts under the influence of a returnspring 73 and sets off the alarm. The alarm may be an audible whistle, a flashing light, or a remote indicator.

FIG. 3 is a transverse section, taken along line 33 of FIG. 1, of the pool 10 and its safety cover with support platform 11, frame 27, floatation members 30 and guide rods 40. The conduit terminates, inside the pool, in a flexible section 26a communicating with the tubular frame 27 through which the air is distributed to the floatation pillows 30 and on which the platform 11 rests.

The vertical guide bars 40 are embedded in the base of the pool, near its side-walls, and co-operative with bearings 41 in restricing the pool cover to travel along a vertical path without touching the pool. Each bearing 41 is formed by piercing a circular hole through a length of metallic strap and wrapping the end furthest from the hole around a section of the support frame 27. Rigid alignment between the bearing 41 and frame 27 is assured by welding or cementing the two together.

The floatation members 30 are constructed from rubber sheet, in the manner oflayflat tubing, by superimposing two sheets similar in size and shape and cementing their edges into an air-tight seam. By means of this construction a self-collapsing tendency is imparted to the floatation pillows; i.e., upon opening the release valve to the atmosphere the component sheets of the member 30 relax into close contact with oneanother, thereby expelling the initially contained air. This feature assures the maximum possible differential buoyancy for the floatation members between their inflated and deflated conditions.

The floatation members are secured to the frame by flexible straps 35, suitably of rubber or plastic, as shown in FIG. 3. These straps encompass the frame tubes 27 and pass through, or clamp on, the seams of the floatation members 30 adjoining the frame. When slack, the floatation members 30 are trapped in the space formed by the frame 27, the platform 11 and the bottom of the pool; in the inflated condition they trans fer their excess buoyancy to the platform by bearing against it from below.

FIG. 5 illustrates, in base view, a pool safety cover for a rectangular basin, incorporating a platform 11 similar to the equivalent element shown in FIGS. 3 and 4. The platform is supported on a frame 127 comprising a continuous, tubular member conforming to the inside perimeter of the pool, braced by a centrally located tube 127a, into which the compressed-air supply hose 26 is led. The frame 127 interconnects the floatation members 30, six in number, each of which is supplied with air via a nozzle 31.

The guide bars 40 employed in conjunction with the pool cover are engaged by bearing members 141, formed by contouring a section of metal bar into a pair of adjoining rings in planes rotated 90 relative one to another; one of these rings engaging the tubular frame 127 in secure frictional bond, the other providing a loose fit over the diameter of the guide bar 40.

A modified safety pool cover shown in FIGS. 6 and 7 employs a substantially rigid platform 111 provided with a plurality of apertures or passageways 41 for permitting the flow of water therethrough. The floatation members 130 are of the type disclosed in connection with FIGS. l5 and same are suitably connected to the conduit 26 for receiving air from a compressor. Such members 130 are fixedly secured in a suitable manner to the bottom of the platform 111 and extend along the peripheral edge 47. If necessary, depending on the platforms weight, additional floatation members 130 may also be provided centrally of the perepheral edge 47 and extend longitudinally and/or transversely of the platform 111. These members may be suitably interconnected with the peripheral floatation members or have other conduit means for transferring air to and from said members.

Another embodiment of the invention, specifically adapted to the protection of pools with increased depth over a portion of their area, is illustrated in FIGS. 8, 9 and 10. Such pools are commonly employed to provide a shallow wading section for children, or, alternately, when a diving board is fitted and it is necessary to provide a depth greater than normal for safe use by divers. In either case one section of the pool bottom lies at a lower elevation than the other and the submerged pool cover must conform, lest it obviate the purpose for which the step in the pool had originally been provided. Yet the pool cover must, upon inflation of its flotation members, be capable of rising into the surface of the pool as a flat horizontal platform.

The pool safety cover 101, adapted to such use, comprises two separate platforms, 2lla and 211b, supported on their frames 57 and 67 and interconnected by hinged platform segment 211C, with its own frame 77 overlying the region of transition between the deeper and shallower portions of the pool. The frames 57 and 77 are hinged at a pivot 70, while the frame 67 attaches to the frame 77 by means of springs 60, which not only permit relative rotation but take up the differential between the submerged and deployed lengths of the pool cover.

The decking from which the platforms 211 are constructed is a perforated rigid sheet, the frames 57 and 67 are tubular and perform the function of air manifolds; frame 57 being interconnected with the air plenum 25 via conduit 26, while air flow to, and from, the frame 67 is through the conduit 126 and frame 57. Four floatation members are provided; 230a and 230 support, respectively, the platforms 211a and 211b, an additional floatation member 232 accepts the weight of the outboard extensions 58 of the frame 57 and a similar member 233 supports the frame 77 and its deck 21 10.

FIG. shows some of the detailsof the spring joint between frames 67 and 77, including the nozzle 131 through which air is supplied to the floatation bag 233 from frame 67 and the support brackets 48 on which the platforms 211 are secured in rigid relationship with their supporting frames.

FIG. 9 shows the safety cover 101, from its lower surface and in the deployed position, with the perimeter tubes of the three sub-frames aligned and the spring 60 compressed; FIG. 10 is taken along section line 10-10 of this view.

The detailed construction ofa nozzle 231, for supply ing air to a floatation member 30, is illustrated in FIG. 11. The nozzle constructed in the manner of a union, with a flanged, tubular member 80 secured into a hole drilled in frame-tube 27 by cement or solder, a nut 82 entrapped on member 80; a second member 81 being cemented to floatation pillow 30 at an integral flange 181. The outer diameter of the member 81 is threaded to receive the nut 82, which, upon tightening, brings the ends of members 80 and 81 into leak-tight engagement. thereby completing the conduit nozzle 23].

An alternative structure for accomplishing the simultaneous rotational and axial relative motions ofa multiple-platform pool cover is illustrated in FIG. 13. A hinge-link 270 is shown, in the form of a triple-bladed yoke with a central spine 279. Slots 273 and 274 are milled into the blades of the link 270 at either end to accept pins 271 and 272 located in tines at the ends of sub-frames 227 and 227a. The sub-frames are shown in the positions they would assume resting upon the bottom of a pool with dual depth. FIG. 12 is a plan view of the flexible connection of FIG. 13; FIG. 14 is another sideview of the same mechanism, representing the floating position of the pool cover, with the subframes 227 and 227a in horizontal alignment with each other and the link 270.

FIG. 15 is a sectional view ofa pool cover of the invention in the floating, or deployed, position. It illustrates the manner in which such a cover may be secured to the upper ends of guide rods 240. The locking of the pool cover in the deployed position is particularly useful on occasions when the pool is to be left unattended for a long period of time and it is desired to prevent the accidental, or deliberate, sinking of the cover. The guide rods 240 are provided with shoulders and threaded extensions of a smaller diameter, with nuts 43 engaging the threaded portion. When the pool cover floats into the deployed position, with its platform 11 substantially level with the edge of the pool, its guide bearings 41 are arranged to ride on the threaded extensions of the guide rods, permitting a C-washer 44 to be interposed between the shoulder of each guide rod and the lower surface of the corresponding bearing 41, thereby preventing the latter from moving downward. The lock is secured by tightening the nut against the upper surface of the bearing, trapping the washer 44 between the bearing and the guide rod.

Another anchoring device incorporates the structure illustrated on FIGS. 16 and 17. The guide rod is provided with a cap 148 attached to the pool wall. The cap 148 limits the upward motion of the pool cover 100. The pool cover may be locked in the upmost position by inserting locking pin 149, located at hand by means of chain 49, through a mating hole drilled into the guide rod 140.

FIG. 18 illustrates an alternative embodiment of the release, that component of the control chassis 20 which permits the discharge of compressed air from the floatation chambers of the pool cover and causes the pool cover to sink into the inactive position.

A valve-body 99 is provided with a nozzle 98, communicating with the plenum chamber 25, and another nozzle 91, open to the atmosphere. An orifice-plate 92 is interposed between these nozzles and is normally covered by a seal-plate 93 mounted on stem 94. The stem 94 is biased, by a spring 95, to maintain tight contact between the seal-plate and the orifice-plate. A handle 96 is hinged to the body 99 in such a manner that depressing the handle causes the stem 94 to move further into the body of the valve, thereby uncovering the perforations in the orifice-plate 92 and placing the intake and discharge nozzles, 98 and 91 respectively, into communication with one another. This permits the compressed air in the plenum 25, and in the floatation members connected therewith through conduit 26, to escape. As long as the handle 96 is held in the depressed position, the buoyancy ofthe pool cover will be continuously reduced, until the pool cover sinks below the surface of the water in the pool and settles to the bottom; the reduction in buoyant volume being aided by the self-collapsing feature of the floatation members themselves.

While the pools shown in the drawings are of masonry construction and rectangular in plan, the safety pool cover of the invention is equally adaptable to above-ground pools, to pools of differing shapes, bottom configurations, and constructions without departing from the teachings set forth herein. Similarly buoyancy may be provided by gases other than air and the inflating pressure may be derived from pre-compressed volumes of gas commercially available in high-pressure cylinders.

Other modifications of details of construction and of materials from those set forth above may also suggest themselves to one skilled in the art, once exposed to the foregoing disclosure.

What is claimed is:

l. A safety device for swimming pools, comprising:

a platform, substantially conforming to the water surface of said pool;

a rigid, tubular frame for supporting said platform;

buoyancy means, including at least one floatation bag fabricated from impermeable, elastic sheet material, secured to the underside of said platform; gas compression means;

conduit means, interconnecting said gas compression means and said buoyancy means;

control means, for governing the flow of compressed gas through said conduit means, whereby said floatation bags may be caused to expand and raise said platform to the surface of said liquid in said pool, thereby preventing access to the pool; and

release means communicating with said conduit means, for venting compressed gas retained in said floatation bags to the atmosphere; whereby said platform may be caused to sink to the bottom of the pool, thereby permitting access thereto.

2. The safety cover defined in claim 1, wherein said conduit means include:

a plenum chamber for compressed gas;

first channel means interconnecting said gas compression means with said plenum chamber; second channel means interconnecting said control means with said plenum chamber;

third channel means interconnecting said release means with said plenum chamber;

first nozzle means, for admission of compressed gas into said tubular frame;

second nozzle means interconnecting each of said flotation bags with said tubular frame; and

fourth channel means interconnecting said plenum with said first nozzle means. 3. The safety pool cover defined in claim I, in which said gas compression means include an air compressor and a plenum chamber for compressed air.

4. The safety pool cover defined in claim 1, in which said control means include a valve in said conduit means.

5. The safety pool cover defined in claim 1, in which said release means include a manually operated vent valve.

6. The safety pool cover defined in claim 3, further comprising alarm means sensitive to the pressure level of gas retained in said bags, for providing a signal when said pressure level drops below a pre-determined value; thereby indicating a potentially unsafe condition of the pool cover.

7. The safety pool cover defined in claim 1, further comprising a control chassis for supporting said gas compression means, said control means and said release means, thereby permitting said components to be located at some distance from the pool.

8. The safety pool cover defined in claim 1, further comprising:

guide means, including at least four vertical guide bars within the water volume of said pool, extending from the bottom thereof to above the normal water level; said guide bars cooperating with bearing means, secured to said tubular frame, in restraining the platform into substantially horizontal alignment during travel between the bottom of the pool and the water surface.

9. The safety pool cover defined in claim 8, wherein said guide bars are cylindrical, elongated members and said bearing means comprise a pluralty of cylindrical bushings rigidly affixed to said frame, each of said bushings being adapted to slideably engage one of said guide bars.

10. The safety pool cover defined in claim 8, further comprising anchor means, for securing said bearing means to said guide means with said platform at the upper limit of its travel; thereby preventing the platform from sinking to the bottom of the pool upon actuation of said release means, or accidental venting of pressurized gas from said floatation bags.

ll. The safety pool cover defined in claim 1, wherein said platform is fabricated from a rigid, foraminous sheet material.

12. The safety pool cover defined in claim 1, wherein said platform is fabricated from expanded metal mesh.

13. A safety pool cover adapted to swimming pools provided with substantially vertical perimeter walls and a segmented bottom contour with at least two differing elevations, comprising:

sectioned platform means, including a plurality of abutting sections, substantially conforming to the shape of the water surface in said pool;

support means, including a rigid tubular frame for each of said sections;

a plurality of floatation bags fabricated from imper rneable, elastic sheet material, at least one of said floatation bags secured to the underside of each of said sections;

gas compression means;

channel means, interconnecting said gas compression means with a particular one of said rigid, tubular frames;

conduit means, interconnecting the other tubular frames with said particular one;

nozzle means, interconnecting each of said floatation bags with a tubular frame;

link means, for permitting relative pivotal and spatial movement between abutting pairs of said sections;

control means, for governing flow of compressed gas into said channel means, whereby said floatation bags may be caused to expand and raise said platform means to the surface of said water in the pool with said abutting sections aligned; and

release means, communicating with said channel means, for venting compressed gas retained in said floatation bags, whereby said platform means may be caused to sink to the bottom of the pool with each of said abutting sections resting on a cone sponding segment of said pool bottom; and the ac tuation of said control means and said release means, alternately, preventing and permitting access to the pool.

14. The safety pool cover defined in claim 13, further comprising:

guide means, including at least four vertical guide bars within the water volume of said pool, extending from the bottom thereof to above the normal water level; said guide bars cooperating with bearing means, secured to said platfrom means, in restraining the abutting sections into progressively horizontal alignment during travel from the bottom of the pool to the water surface.

15. A safety device for swimming pools, comprising:

a rigid platform, substantially conforming to the water surface of said pool;

10 platform to the surface of said liquid in said pool, thereby preventing access to the pool; and release means communicating with said conduit means, for venting compressed gas retained in said floatation bags to the atomosphere; whereby said platform may be caused to sink to the bottom of the pool, thereby permitting access thereto. 

1. A safety device for swimming pools, comprising: a platform, substantially conforming to the water surface of said pool; a rigid, tubular frame for supporting said platform; buoyancy means, including at least one floatation bag fabricated from impermeable, elastic sheet material, secured to the underside of said platform; gas compression means; conduit means, interconnecting said gas compression means and said buoyancy means; control means, for governing the flow of compressed gas through said conduit means, whereby said floatation bags may be caused to expand and raise said platform to the surface of said liquid in said pool, thereby preventing access to the pool; and release means communicating with said conduit means, for venting compressed gas retained in said floatation bags to the atmosphere; whereby said platform may be caused to sink to the bottom of the pool, thereby permitting access thereto.
 2. The safety cover defined in claim 1, wherein said conduit means include: a plenum chamber for compressed gas; first channel means interconnecting said gas compression means with said plenum chamber; second channel means interconnecting said control means with said plenum chamber; third channel means interconnecting said release means with said plenum chamber; first nozzle means, for admission of compressed gas into said tubular frame; second nozzle means interconnecting each of said flotation bags with said tubular frame; and fourth channel means interconnecting said plenum with said first nozzle means.
 3. The safety pool cover defined in claim 1, in which said gas compression means include an air compressor and a plenum chamber for compressed air.
 4. The safety pool cover defined in claim 1, in which said control means include a valve in said conduit means.
 5. The safety pool cover defined in claim 1, in which said release means include a manually operated vent valve.
 6. The safety pool cover defined in claim 3, further comprising alarm means sensitive to the pressure level of gas retained in said bags, for providing a signal when said pressure level drops below a pre-determined value; thereby indicating a potentially unsafe condition of the pool cover.
 7. The safety pool cover defined in claim 1, further comprising a control chassis for supporting said gas compression means, said control means and said release means, thereby permitting said components to be located at some distance from the pool.
 8. The safety pool cover defined in claim 1, further comprising: guide means, including at least four vertical guide bars within the water volume of said pool, extending from the bottom thereof to above the normal water level; said guide bars cooperating with bearing means, secured to said tubular frame, in restraining the platform into substantially horizontal alignment during travel between the bottom of the pool and the water surface.
 9. The saFety pool cover defined in claim 8, wherein said guide bars are cylindrical, elongated members and said bearing means comprise a pluralty of cylindrical bushings rigidly affixed to said frame, each of said bushings being adapted to slideably engage one of said guide bars.
 10. The safety pool cover defined in claim 8, further comprising anchor means, for securing said bearing means to said guide means with said platform at the upper limit of its travel; thereby preventing the platform from sinking to the bottom of the pool upon actuation of said release means, or accidental venting of pressurized gas from said floatation bags.
 11. The safety pool cover defined in claim 1, wherein said platform is fabricated from a rigid, foraminous sheet material.
 12. The safety pool cover defined in claim 1, wherein said platform is fabricated from expanded metal mesh.
 13. A safety pool cover adapted to swimming pools provided with substantially vertical perimeter walls and a segmented bottom contour with at least two differing elevations, comprising: sectioned platform means, including a plurality of abutting sections, substantially conforming to the shape of the water surface in said pool; support means, including a rigid tubular frame for each of said sections; a plurality of floatation bags fabricated from impermeable, elastic sheet material, at least one of said floatation bags secured to the underside of each of said sections; gas compression means; channel means, interconnecting said gas compression means with a particular one of said rigid, tubular frames; conduit means, interconnecting the other tubular frames with said particular one; nozzle means, interconnecting each of said floatation bags with a tubular frame; link means, for permitting relative pivotal and spatial movement between abutting pairs of said sections; control means, for governing flow of compressed gas into said channel means, whereby said floatation bags may be caused to expand and raise said platform means to the surface of said water in the pool with said abutting sections aligned; and release means, communicating with said channel means, for venting compressed gas retained in said floatation bags, whereby said platform means may be caused to sink to the bottom of the pool with each of said abutting sections resting on a corresponding segment of said pool bottom; and the actuation of said control means and said release means, alternately, preventing and permitting access to the pool.
 14. The safety pool cover defined in claim 13, further comprising: guide means, including at least four vertical guide bars within the water volume of said pool, extending from the bottom thereof to above the normal water level; said guide bars cooperating with bearing means, secured to said platfrom means, in restraining the abutting sections into progressively horizontal alignment during travel from the bottom of the pool to the water surface.
 15. A safety device for swimming pools, comprising: a rigid platform, substantially conforming to the water surface of said pool; buoyancy means, including at least one floatation bag fabricated from impermeable, elastic sheet material, secured to the underside of said platform; gas compression means; conduit means, interconnecting said gas compression means and said buoyancy means; control means, for governing the flow of compressed gas through said conduit means, whereby said floatation bags may be caused to expand and raise said platform to the surface of said liquid in said pool, thereby preventing access to the pool; and release means communicating with said conduit means, for venting compressed gas retained in said floatation bags to the atomosphere; whereby said platform may be caused to sink to the bottom of the pool, thereby permitting access thereto. 